The present invention relates to a semiconductor apparatus which is used in an AC-DC converter that converts an alternating-current power into a direct-current power, and in particular, to a semiconductor apparatus for automotive use, which is used in the AC-DC converter that converts the alternating-current power output from an alternator into the direct-current power and strongly requires the long thermal fatigue life against the change of a temperature to the semiconductor apparatus.
A semiconductor apparatus used in an AC-DC converter for automotive use inhibits a semiconductor chip composing the AC-DC converter from raising its temperature when converting an alternating-current power output from an alternator into a direct-current power, by radiating heat generated in the semiconductor chip mainly through a radiator plate.
In recent years, a 20° C. higher operating temperature has been required to an alternator for automotive use than a request value of about 180° C. for the conventional use operating temperature. When a semiconductor apparatus used in the AC-DC converter is operated under such a high operating temperature, the thermal fatigue life of the semiconductor apparatus may end in comparatively short thermal fatigue life cycle times.
For this reason, JP-A-2005-340267 discloses a technology on a semiconductor apparatus which is used in an AC-DC converter for automotive use, prevents a semiconductor element from causing a crack in a cooling step after joint assembly or a thermal shock test, and shows the superior thermal fatigue life which is caused by the repeated passing/interception of an electric current to/against the semiconductor element. The semiconductor apparatus has a configuration of: making a thin sheet member with low thermal expansion made from a clad material of Cu/Fe—Ni alloy/Cu having a thermal expansion coefficient of 10 PPM (10×10−6 (1/° C.)) or lower inserted between the semiconductor element and both of electrode terminals through jointing members respectively, as a stress relaxation material; and forming the thin sheet member with low thermal expansion so that the outline dimension in a lead electrode terminal side can be smaller than that of an electrode face of the semiconductor element, and the outline dimension in a base electrode terminal side can be larger than that of an electrode face of the semiconductor element.
However, a semiconductor apparatus which has a configuration disclosed in JP-A-2005-340267 and used in an AC-DC converter for automotive use has had a problem that the thermal fatigue life of a jointing member ends in a comparatively few thermal fatigue life cycle times and the thermal fatigue life of the semiconductor apparatus ends in a comparatively short period, because the jointing member has a thermal expansion coefficient greatly different from those of a semiconductor chip, a lead electrode and a support electrode, and the jointing member that joints the semiconductor chip is exposed to a high maximum temperature and receives a great temperature change, which generates heat when converting an alternating-current power output from an alternator into a direct-current power.
An object of the present invention is to provide a semiconductor apparatus which is provided with a semiconductor chip used in an AC-DC converter that converts an alternating-current power to a direct-current power, effectively transfers heat generated in the semiconductor chip to a support electrode to radiate the heat, lowers the maximum temperature on a jointing member existing between a semiconductor element and an electrode terminal, reduces the width of the temperature change, and thereby improves the thermal fatigue life against the temperature change.